This invention relates to an apparatus for inserting a catheter into the ventricles of the brain.
Shunt systems are required in the treatment of hydrocephalus for draining excess cerebrospinal fluid from the ventricles of the brain either to the right atrium of the heart or to the peritoneum. One such shunt system is described in two recent patents, both entitled "Low Profile Shunt System," U.S. Pat. Nos. 4,364,395 issued Dec. 21, 1982 and 4,464,168 issued Aug. 7, 1984. Both patents are assigned to the same assignee as the present invention and are herein incorporated by reference.
One component of a hydrocephalus shunt system, the ventricular catheter, must be inserted through a hole in the skull and through brain tissue so that the tip of the catheter lies in the ventricle of the brain. The ventricular catheter is made from a soft silicone material and must be supported in order to ensure proper insertion into the brain tissue. If the ventricular catheter is supplied as a separate component of the shunt system, an internal stylet may be inserted into the open end of the catheter to provide support during insertion. However a shunt system which consists of separate components (ventricular catheter, valve, and atrial or peritoneal catheter) is more difficult to implant because it requires connecting the separate components during the surgical procedure.
A one piece shunt system is also available which includes all of the components discussed above. However, this design has no open end for insertion of the supporting internal stylet into the ventricular catheter. One method of inserting a one piece shunt system into the ventricle is to first insert into the brain a rigid rod of approximately the same as or slightly larger diameter than the catheter. The rod is then removed and the catheter is quickly pushed through the path created by the rod. One of the problems associated with this method is that it is still difficult to push the catheter into the proper position in the ventricle because the catheter is unsupported when it is inserted.
Another method of inserting the one piece shunt ventricular catheter is to use an external introducer. External introducers generally consist of a stylet which passes through and protrudes from a cannula. The tip of the stylet is inserted through one of the proximal drainage holes in the catheter in order to internally support the catheter tip during insertion into the brain. The cannula is positioned adjacent the length of the catheter. After insertion of the introducer and catheter into the brain, the stylet is retracted, releasing the tip of the catheter. The cannula is then retracted from the brain.
The problem with the introducers presently available is that the introducer and catheter assembly has a relatively large profile in cross-section. In these assemblies, the catheter tip is held at an angle with respect to the rest of the catheter and there is also a space between the distal portion of the catheter and the cannula. Thus the cross-sectional profile of the connected introducer and catheter is larger than the sum of their individual profiles, causing unnecessary displacement of brain tissue. It is desirable to minimize the cross-sectional profile of the introducer and catheter assembly to reduce the trauma to the brain caused by brain tissue being displaced during the insertion of the assembly.